<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
        <script src="../js/vue.js"></script>
	</head>
	<body>
		<div id="root">
          姓:<input type="text" v-model="firstName"><br> <br>
          名：<input type="text" v-model="lastName"><br> <br>
            全名：<span>{{fullName}}}</span><br> <br>
        </div>
		
	</body>
    <script type="text/javascript">
        Vue.config.productionTip = false
        new Vue({
			el:'#root',
			data:{
				firstName:'张',
                lastName:'三',
                fullName:'张-三'
                },
            watch:{
                firstName(newValue,oldValue){
                    setTimeout(()=>{
                        this.fullName=newValue+'-'+this.lastName
                    },1000)

                },
                lastName(val){
                    this.fullName=this.firstName+'-'+val
                }
            }

		})
    </script>
</html>
